1. Field of the Invention
The invention relates to a method of manufacturing a semiconductor structure, and more particularly to a manufacturing method of a bump structure.
2. Description of Related Art
Flip chip interconnection technology is a packaging technique for connecting a die to a circuit board, which mainly is forming a plurality of bumps on a plurality of pads of the die. Afterwards, the die is flipped over and the bumps are used for connecting the pads of the die to terminals on the circuit board, so that the die is electrically connected to the circuit board through the bumps. Generally, there are several types of bumps, such as solder bumps, gold bumps, copper bumps, conductive polymer bumps, polymer bumps and so on.
FIG. 1A is a cross-sectional view of a conventional gold bump, and FIG. 1B is a top view of the conventional gold bump. As indicated in FIG. 1A and FIG. 1B, a conventional gold bump structure is suitable to be disposed on a die 110 and a plurality of aluminum pads 120 (only one shown in FIGS. 1A and 1B) and a passivation layer 130 have already formed on the die 110. The passivation layer 130 has a plurality of openings 130a exposing a portion of each of the aluminum pads 120 respectively. Additionally, the conventional gold bump structure includes an under ball metal (UBM) layer 140 and a gold bump 150. The UBM layer 140 is disposed within the opening 130a and covers a portion of the passivation layer 130. The gold bump 150 is disposed on the UBM layer 140. The gold bump 150 covers the UBM layer 140 on a portion of the passivation layer 130. As a result, an annular protrusion 150a is formed on the gold bump 150, which is the so-called wall effect. However, the annular protrusion 150a would affect the bonding strength between the gold bump 150 and other carriers (not shown). Moreover, since the UBM layer 140 is merely disposed beneath the gold bump 150, when cracks occur between the UBM layer 140 and the gold bump 150, or between the UBM layer 140 and the passivation layer 130, the under cut effect is prone to occur in the conventional gold bump structure.